Merge pull request #8 from cozodb/dev

fixes #3

src/parse/query.rs

@@ -198,8 +198,9 @@ pub(crate) fn parse_query(
                 algo_impl.process_options(&mut options, span)?;
                 let arity = algo_impl.arity(&options, &head, span)?;
 
+                ensure!(arity != 0, EmptyRowForConstRule(span));
                 ensure!(
-                    arity == 0 || head.is_empty() || arity == head.len(),
+                    head.is_empty() || arity == head.len(),
                     FixedRuleHeadArityMismatch(arity, head.len(), span)
                 );
                 progs.insert(
@@ -764,6 +765,11 @@ fn parse_algo_rule(
 #[diagnostic(help("Expected arity: {0}, number of arguments given: {1}"))]
 struct FixedRuleHeadArityMismatch(usize, usize, #[label] SourceSpan);
 
+#[derive(Debug, Error, Diagnostic)]
+#[error("Encountered empty row for constant rule")]
+#[diagnostic(code(parser::const_rule_empty_row))]
+struct EmptyRowForConstRule(#[label] SourceSpan);
+
 fn make_empty_const_rule(prog: &mut InputProgram, bindings: &[Symbol]) {
     let entry_symbol = Symbol::new(PROG_ENTRY, Default::default());
     let mut options = BTreeMap::new();

tests/air_routes.rs

@@ -159,6 +159,18 @@ fn dfs() {
     dbg!(dfs.elapsed());
 }
 
+#[test]
+fn empty() {
+    check_db();
+    let res = TEST_DB.run_script(
+        r#"
+        ?[id, name] <- [[]]
+    "#,
+        &Default::default(),
+    );
+    assert!(res.is_err());
+}
+
 #[test]
 fn bfs() {
     check_db();